horse's body language

What dose it mean when a colt rase his head and show his teath like smiling

It's called the Flehmen Response.

http://www.bloodhorse.com/horse-raci...onse-in-horses

It supposedly helps them analyze smells better.

Seem a few geldings do that when a weird smell catches their noses. Like when another horse has just had a bath & still smells like products.

My old mare used to do that all the time! We called it her smile

But yeah, analyze smells better

He's lifting his top lip up to his nose so he can smell better.

He is smiling, because he loves you :)

Nah, just kidding. Its a way to help smell, have you ever given your horse a peppermint, or they've smelt something strong? That is normally when they do it.